Questions from a newcomer

Hi -
I would like to learn know about an implementation of Scheme which runs
on VAX VMS 4.x and an implementation which runs on a 68000 machine
(especially Amiga, Macintosh Plus, Sage/Stride, or Atari 1040ST). I
have seen a reference to Scheme 312 which sounded interesting.
I have also seen a reference to "Chez Scheme" for VAX BSD 4.2++ which I
would like to know more about.
I am especially interested "native" implementations (not implemented on
top of another Lisp), versions with a compiler, and versions which are
public domain. I have purchased TI's PC Scheme for my IBM AT.
I am interested in Scheme because I think it may run reasonably well on
a micro I can afford to have at home. I have a Sage II now, but I am
considering another 68000 machine. I am also hoping that Scheme will
be a simple, easy to implement Lisp which is not thundering towards
commercialization.
I tried Golden Common Lisp on ATs and was disappointed in the
unwieldiness.
We have Common Lisp (DEC Lisp and NIL) on the VAXen I use at work,
but I would like to investigate Scheme as an alternative.
- Thanks
jim mullens
oak ridge national laboratory